As I was making my dear daughter a new apron for Christmas - and the directions called for a 'narrow hem'. Directions - if any more are given, usually say to "press under 1/4" then turn and press under 1/4" again and topstitch.
Long ago - when making many silky type blouses in my custom dressmaking years, I came up with 'my way' of doing this - which I feel is MUCH easier - especially since you won't burn your fingers.
1. Fold the right side to the wrong side a generous 1/2" at the ironing board, and press.
2. AT THE MACHINE, with the wrong side up, simply tuck under the raw edge as you stitch - a few inches at a time. Do NOT try to do this and pin it all to begin with. If you have the 'needle down' feature on your machine - make sure to use it to hold things in place each time you stop to turn under more fabric. See the photo below for a real 'picture' of how I do this.
Be advised, that the thread in your BOBBIN is what will show on the outside of the garment.